(a) Field of the Invention
The present invention relates to a control device of a light emitting device formed of light emitting diodes (LEDs). Particularly, it relates to a control device that drives a light emitting device including a plurality of LED rows formed of a plurality of LEDs connected in series.
(b) Description of the Related Art
A light emitting device may display an image, or may be used as a light source of a display device such as a liquid crystal display (LCD). Particularly, a light emitting device formed of a plurality of LEDs is widely used as a back light of an LED display device. The LED light emitting device includes a plurality of LED rows formed by a plurality of LEDs arranged in series and a converter that supplies an output voltage to each of the plurality of LED rows. The output voltage is supplied to at one end of each of the plurality of LED rows, and a constant current source that regulates a current flowing to each of the plurality of LED rows is connected to the other end thereof. When a current flows to the LED and light is emitted, a voltage drop is generated along a direction of a current at lateral ends of the LED. In addition, voltage drops of all LEDs are not constant due to characteristics thereof. Therefore, the converter supplies a sufficient voltage to each of the plurality of LED rows so that each LED of the LED rows can emit light regardless of the voltage drop. A constant current source includes a synch current source, and the synch current source is connected to each of the plurality of LEDs to maintain a constant current. When a voltage is applied to the synch current source, power is consumed, and therefore it is preferred to apply the lowest voltage to the synch current source.
However, a voltage that is higher than a predetermined reference voltage is required for driving the synch current source, and therefore the voltage applied to the synch current source cannot be decreased without limit.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.